1. Field of the Invention
The present invention relates generally to a light delivery system useable for medical treatment, such as light therapy for the treatment of proliferative diseases.
2. Description of the Related Art
Light therapy includes photodynamic therapy (PDT) which is a process whereby light of a specific wavelength or waveband is directed toward a target cell or cells that have been rendered photosensitive through the administration of a photo-reactive, photo-initiating, or photosensitizing agent. This photo-reactive agent has a characteristic light absorption waveband and is commonly administered to a patient via intravenous injection, oral administration, or by local delivery to the treatment site. It is known that abnormal cells in the body may selectively absorb certain photo-reactive agents to a greater extent than normal for healthy cells. Once the abnormal cells have absorbed and/or molecularly joined with the photo-reactive agent, the abnormal cells can then be treated by exposing those cells to light of an appropriate wavelength or waveband that substantially corresponds to the absorption wavelength or waveband of the photo-reactive agent.
The objective of PDT may be either diagnostic or therapeutic. In diagnostic applications, the wavelength of light is selected to cause the photo-reactive agent to fluoresce as a means to acquire information about the targeted cells without damaging the targeted cells. In therapeutic applications, the wavelength of light delivered to the targeted cells treated with the photo-reactive agent causes the agent to undergo a photochemical reaction with oxygen in the localized targeted cells, to yield free radical species (such as singlet oxygen), which cause localized cell lysis or necrosis.
PDT has therefore proven to be an effective oncology treatment for destroying targeted cancerous cells. In addition, PDT has been proposed as a treatment for other ailments, some of which are described in Applicant's co-pending patent application U.S. Publication No. 2005/0228260 (U.S. patent application Ser. No. 10/799,357, which is hereinafter referred to as the '357 patent application).
One type of light delivery system used for PDT treatments comprises the delivery of light from a light source, such as a laser, to the targeted cells using a single optical fiber delivery system with special light-diffusing tips. This type of light delivery system may further include single optical fiber cylindrical diffusers, spherical diffusers, micro-lensing systems, an over-the-wire cylindrical diffusing multi-optical fiber catheter, and a light-diffusing optical fiber guidewire. This light delivery system generally employs a remotely disposed high-powered laser or solid state laser diode array, coupled to optical fibers for delivery of the light to the targeted cells. However, the use of laser light sources has several drawbacks, such as relatively high capital costs, relatively large size equipment, complex operating procedures, and safety issues in working with and around high-powered lasers.
The '357 patent application addresses some of these concerns and also addresses the desire to develop a light-generating apparatus that can be secured within a blood vessel or other orifice. The securing mechanism of such an apparatus would also be capable of removing light absorbent or light blocking materials, such as blood, tissue, or another object from the light path between the targeted cells and the light transmitters. Securing the apparatus within a blood vessel, for example, can be achieved with an inflatable balloon catheter that matches the diameter of the blood vessel when the balloon is inflated.
An introducing sheath having a lumen extending therethrough to create a passageway for insertion of other instruments into a patient's body through the sheath may be used with the light delivery system. One type of introducing sheath is described in another one of Applicant's co-pending patent applications, PCT Application No. PCT/US2005/032851. In general, this type of introducing sheath surrounds a penetrating device, which is introduced into the body and then removed, leaving the sheath behind as a passageway. One such instrument that can be inserted through the sheath is a light catheter for PDT treatment.
The light source for the light system used for PDT treatments may also be light emitting diodes (LEDs). Arranged LEDs form a light bar for the light system, where the LEDs may be either wire bonded or electrically coupled utilizing a “flip chip” technique that is used in arranging other types of semiconductor chips on a conductive substrate. Various arrangements and configurations of LEDs are described in U.S. Pat. Nos. 6,958,498; 6,784,460; and 6,445,011; and also in the '357 patent application.